Long-chain branched polypropylenes by electron beam irradiation and their rheological properties
Long-chain branched polypropylenes by electron beam irradiation and their rheological properties
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DOI：
10.1021/ma030579w
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发表时间：
2004-12-14
期刊：
影响因子：
5.5
通讯作者：
Lunkwitz, K
中科院分区：
文献类型：
--
作者：
Auhl, D;Stange, J;Lunkwitz, K
本文的目的是研究如何用电子束辐照改性线性聚丙烯的分子结构。为此目的，用不同剂量照射线性前体。样品进行了分析，通过尺寸排阻色谱结合光散射检测器。随着辐照剂量的增加，分子量减少，长链分支的数目增加，此外，得出的结论相对于所获得的长链分支的拓扑结构从辐照样品的零剪切粘度的摩尔质量依赖性，这明显偏离线性聚丙烯。实验结果可以解释为，在低剂量下，很少但很长的分支出现。在较高剂量下，每个分子存在更多和更短的分支。拉伸实验清楚地显示出应变硬化行为随辐照剂量的变化，这与剪切测量得出的结构变化一致。从流变学和他们的解释结果表明两个特点。首先，在辐照聚丙烯上进行的流变学实验对于长链支化比基于尺寸排阻色谱结合光散射的经典表征方法敏感得多。其次，从线性和辐照聚丙烯的流变行为的比较，可以得出一些结论，关于所产生的长链分支的拓扑结构。
The aim of this paper is to investigate how the molecular structure of linear polypropylenes can be modified by electron beam irradiation. For this purpose a linear precursor was irradiated with different doses. The samples were analyzed by size-exclusion chromatography coupled with a light scattering detector. With increasing doses, a reduction of molar mass and an increasing number of long-chain branches were found. Moreover, conclusions with respect to the topography of the long-chain branches obtained were drawn from the molar mass dependence of the zero shear viscosity of the irradiated samples, which deviates significantly from that of linear polypropylenes. The experimental results can be interpreted in a way that at low doses very few but long branches occur. At higher doses more and shorter branches per molecule exist. The elongational experiments clearly exhibit a change of the strain-hardening behavior with irradiation dose, which is in agreement with the structural changes concluded from the shear measurements. The results from rheology and their interpretation demonstrate two features. First, rheological experiments conducted on irradiated polypropylenes are much more sensitive with respect to long-chain branching than the classical characterization methods based on size-exclusion chromatography coupled with light scattering. Second, from a comparison of the rheological behavior of linear and irradiated polypropylenes some conclusions can be drawn regarding the topography of the long-chain branches generated.